Plasma processing method and plasma processing apparatus

ABSTRACT

A plasma processing method according to an exemplary embodiment includes preparing a substrate in a chamber of a plasma processing apparatus. The substrate is disposed on a substrate support in the chamber. The substrate support includes a lower electrode and an electrostatic chuck. The electrostatic chuck is provided on the lower electrode. The plasma processing method further includes applying a positive voltage to a conductive member when plasma is being generated in the chamber for plasma processing on the substrate. The conductive member extends closer to a grounded side wall of the chamber than the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority fromJapanese Patent Application No. 2019-130978 filed on Jul. 16, 2019, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

Exemplary embodiments of the present disclosure relate to a plasmaprocessing method and a plasma processing apparatus.

BACKGROUND

Plasma processing on a substrate is performed using a plasma processingapparatus. A plasma processing apparatus disclosed in Japanese PatentApplication Laid-Open Publication No. 2003-297810 (hereinafter referredto as a “Patent Literature 1”) is known as one type of a plasmaprocessing apparatus. The plasma processing apparatus disclosed inPatent Literature 1 is provided with a chamber, a lower electrode, andan upper electrode. The lower electrode is provided in the chamber. Asubstrate is placed on the lower electrode. The upper electrode isprovided above the lower electrode. In the plasma processing apparatusdisclosed in Patent Literature 1, the upper electrode has a dome shapein order to make plasma density uniform.

SUMMARY

In an exemplary embodiment, a plasma processing method is provided. Theplasma processing method includes preparing a substrate in a chamber ofa plasma processing apparatus. The substrate is disposed on a substratesupport in the chamber. The substrate support includes a lower electrodeand an electrostatic chuck. The electrostatic chuck is provided on thelower electrode. The plasma processing method further includes applyinga positive voltage to a conductive member when plasma is being generatedin the chamber for plasma processing on the substrate. The conductivemember extends closer to a grounded side wall of the chamber than thesubstrate.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, exemplaryembodiments, and features described above, further aspects, exemplaryembodiments, and features will become apparent by reference to thedrawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a plasma processing method according to anexemplary embodiment.

FIG. 2 is a diagram schematically showing a plasma processing apparatusaccording to an exemplary embodiment.

FIG. 3A is a diagram showing an example of a bias, and FIG. 3B is atiming chart showing an example of a potential of a substrate and apotential of a conductive member.

FIG. 4 is a diagram showing another example of the bias.

FIG. 5 is a diagram schematically showing a plasma processing apparatusaccording to another exemplary embodiment.

FIG. 6 is a diagram schematically showing a plasma processing apparatusaccording to still another exemplary embodiment.

FIG. 7 is a timing chart showing an example of the potential of thesubstrate and the potential of the conductive member.

FIG. 8 is a timing chart showing another example of the potential of thesubstrate and the potential of the conductive member.

FIG. 9 is a timing chart showing still another example of the potentialof the substrate and the potential of the conductive member.

FIG. 10 is a timing chart showing still another example of the potentialof the substrate and the potential of the conductive member.

FIG. 11 is a diagram schematically showing a plasma processing apparatusaccording to still another exemplary embodiment.

FIG. 12 is a timing chart showing an example of a potential of asubstrate, a potential of a conductive member, and a potential of anedge ring.

FIG. 13 is a diagram schematically showing a plasma processing apparatusaccording to still another exemplary embodiment.

FIG. 14 is a diagram schematically showing a plasma processing apparatusaccording to still another exemplary embodiment.

DETAILED DESCRIPTION

Hereinafter, various exemplary embodiments will be described.

In an exemplary embodiment, a plasma processing method is provided. Theplasma processing method includes preparing a substrate in a chamber ofa plasma processing apparatus. The substrate is disposed on a substratesupport in the chamber. The substrate support includes a lower electrodeand an electrostatic chuck. The electrostatic chuck is provided on thelower electrode. The plasma processing method further includes applyinga positive voltage to a conductive member when plasma is being generatedin the chamber for plasma processing on the substrate. The conductivemember extends closer to a grounded side wall of the chamber than thesubstrate.

In the embodiment described above, the density of negative ionsincreases near the edge of the substrate by applying a positive voltageto the conductive member. The density of positive ions in plasma isrepresented by the sum of the density of negative ions and the densityof electrons. Therefore, the density of positive ions near the edge ofthe substrate can be adjusted by applying a positive voltage to theconductive member.

In an exemplary embodiment, the substrate is disposed on the substratesupport and in an area surrounded by an edge ring. The edge ring is theconductive member. The plasma processing method further includessupplying a bias to the lower electrode when plasma is being generatedin the chamber for plasma processing on the substrate. The bias is radiofrequency bias power, or a pulsed negative voltage which is periodicallyapplied to the lower electrode. The positive voltage is applied to theedge ring in a period in which the potential of the substrate is equalto or greater than 0, and sets the potential of the edge ring to apotential higher than the potential of the substrate in the period.

In an exemplary embodiment, the substrate is disposed on the substratesupport and in an area surrounded by an edge ring. The conductive memberis electrically separated from the edge ring and extends closer to theside wall of the chamber than the edge ring. The plasma processingmethod further includes supplying a bias to the lower electrode whenplasma is being generated in the chamber for plasma processing on thesubstrate. The bias is radio frequency bias power, or a pulsed negativevoltage which is periodically applied to the lower electrode. Thepositive voltage is applied to the conductive member in a period inwhich the potential of the substrate is negative.

In an exemplary embodiment, the positive voltage may be applied to theconductive member even in the period in which the potential of thesubstrate is equal to or greater than 0.

In an exemplary embodiment, the positive voltage may be a direct-currentvoltage which is continuously applied to the conductive member in boththe period in which the potential of the substrate is negative and theperiod in which the potential of the substrate is equal to or greaterthan 0.

In an exemplary embodiment, the positive voltage which is applied to theconductive member in the period in which the potential of the substrateis negative may be higher than the positive voltage which is applied tothe conductive member in the period in which the period of the substrateis equal to or greater than 0.

In an exemplary embodiment, a positive voltage may be applied to theedge ring to set the potential of the edge ring to a potential higherthan the potential of the substrate in the period in which the potentialof the substrate is equal to or greater than 0.

In an exemplary embodiment, the plasma processing may be plasma etchingon the substrate.

In another exemplary embodiment, a plasma processing apparatus isprovided. The plasma processing apparatus includes a chamber, asubstrate support, and a power source device. The substrate support isprovided in the chamber. The substrate support includes a lowerelectrode and an electrostatic chuck. The electrostatic chuck isprovided on the lower electrode. The power source device is configuredto apply a positive voltage to a conductive member. The conductivemember extends closer to a grounded side wall of the chamber than asubstrate placed on the substrate support.

In an exemplary embodiment, the plasma processing apparatus furtherincludes a bias power source. The bias power source is configured tosupply a bias to the lower electrode when plasma is being generated inthe chamber for plasma processing on the substrate. The bias is radiofrequency bias power, or a pulsed negative voltage which is periodicallyapplied to the lower electrode. The conductive member is an edge ringthat extends to surround the substrate. The power source device isconfigured to apply a positive voltage to the edge ring in a period inwhich the potential of the substrate is equal to or greater than 0, andset the potential of the edge ring to a potential higher than thepotential of the substrate in the period.

In an exemplary embodiment, the conductive member extends closer to theside wall of the chamber than an edge ring extending to surround asubstrate placed on the substrate support. The plasma processingapparatus further includes a bias power source. The bias power source isconfigured to supply a bias to the lower electrode when plasma is beinggenerated in the chamber for plasma processing on the substrate. Thebias is radio frequency bias power, or a pulsed negative voltage whichis periodically applied to the lower electrode. The power source deviceis configured to apply a positive voltage to the conductive member inthe period in which the potential of the substrate is negative.

In an exemplary embodiment, the power source device may be configured toapply a positive voltage to the conductive member even in the period inwhich the potential of the substrate is equal to or greater than 0.

In an exemplary embodiment, the power source device may be configured tocontinuously apply a direct-current voltage as the positive voltage tothe conductive member in both the period in which the potential of thesubstrate is negative and the period in which the potential of thesubstrate is equal to or greater than 0.

In an exemplary embodiment, the positive voltage which is applied to theconductive member in the period in which the potential of the substrateis negative may be higher than the positive voltage which is applied tothe conductive member in the period in which the potential of thesubstrate is equal to or greater than 0.

In an exemplary embodiment, the plasma processing apparatus may furtherinclude an other power source device. The other power source device isconfigured to apply a positive voltage to the edge ring in the period inwhich the potential of the substrate is equal to or greater than 0, toset the potential of the edge ring to a potential higher than thepotential of the substrate in the period in which the potential of thesubstrate is equal to or greater than 0.

Hereinafter, various exemplary embodiments will be described in detailwith reference to the drawings. In the drawing, the same or equivalentportions are denoted by the same reference symbols.

FIG. 1 is a flowchart of a plasma processing method according to anexemplary embodiment. The plasma processing method (hereinafter referredto as a “method MT”) shown in FIG. 1 is applied to a substrate. Theplasma processing in the method MT is, for example, plasma etching onthe substrate. The method MT includes step ST1 and step ST2. In anembodiment, the method MT may further include step STb.

In step ST1, a substrate is prepared in a chamber of a plasma processingapparatus. The substrate may have a disk shape. The substrate isdisposed substantially horizontally on a substrate support in thechamber. In an embodiment, the substrate support includes a lowerelectrode and an electrostatic chuck. The electrostatic chuck isprovided on the lower electrode. The substrate is held by theelectrostatic chuck.

In the method MT, plasma is generated in the chamber in a state wherethe substrate is disposed in the chamber for plasma processing on thesubstrate. Step STb is executed when plasma is being generated in thechamber. In step STb, a bias is supplied to the lower electrode. Thebias is radio frequency bias power, or a pulsed negative voltage whichis periodically applied to the lower electrode.

Step ST2 is executed when plasma is being generated in the chamber. Instep ST2, a positive voltage is applied to a conductive member. Theconductive member extends closer to a grounded side wall of the chamberthan the substrate.

A positive voltage is applied to the conductive member, whereby thedensity of negative ions increases near the edge of the substrate. Thedensity of positive ions in plasma is represented by the sum of thedensity of negative ions and the density of electrons. Therefore, thedensity of positive ions near the edge of the substrate can be adjustedby applying a positive voltage to the conductive member.

Hereinafter, plasma processing apparatuses according to variousexemplary embodiments, which can be used in the execution of the methodMT, will be described. Further, step ST2 which is executed by using eachof the plasma processing apparatuses according to various exemplaryembodiments will also be described.

FIG. 2 is a diagram schematically showing a plasma processing apparatusaccording to an exemplary embodiment. A plasma processing apparatus 1Ashown in FIG. 2 is a capacitively-coupled plasma processing apparatus.The plasma processing apparatus 1A is provided with a chamber 10. Thechamber 10 provides an internal space 10 s therein. The central axis ofthe internal space 10 s is an axis AX extending in the verticaldirection.

In an embodiment, the chamber 10 includes a chamber body 12. The chamberbody 12 has a substantially cylindrical shape. The internal space 10 sis provided in the chamber body 12. The chamber body 12 is made of, forexample, aluminum. The chamber body 12 is electrically grounded. Thatis, the chamber body 12 provides a grounded side wall of the chamber 10.A film having plasma resistance is formed on the inner wall surface ofthe chamber body 12, that is, the wall surface defining the internalspace 10 s. This film may be a ceramic film such as a film formed byanodization or a film formed of yttrium oxide.

A passage 12 p is formed in a side wall of the chamber body 12. Asubstrate W passes through the passage 12 p when it is transferredbetween the internal space 10 s and the outside of the chamber 10. Agate valve 12 g is provided along the side wall of the chamber body 12in order to open and close the passage 12 p.

The plasma processing apparatus 1A further includes a substrate support16. The substrate support 16 is configured to support the substrate Wplaced thereon in the chamber 10. The substrate W has a substantiallydisk shape. The substrate support 16 is supported by a support 17. Thesupport 17 extends upward from a bottom portion of the chamber 10. Thesupport 17 has a substantially cylindrical shape. The support 17 isformed of an insulating material such as quartz.

The substrate support 16 has a lower electrode 18 and an electrostaticchuck 20. The lower electrode 18 and the electrostatic chuck 20 areprovided in the chamber 10. The lower electrode 18 is formed of aconductive material such as aluminum and has a substantially disk shape.

A flow path 18 f is formed in the lower electrode 18. The flow path 18 fis a flow path for a heat exchange medium. As the heat exchange medium,a liquid refrigerant or a refrigerant (for example, Freon) that coolsthe lower electrode 18 by vaporization thereof is used. A heat exchangemedium supply device (for example, a chiller unit) is connected to theflow path 18 f. This supply device is provided outside the chamber 10.The heat exchange medium is supplied to the flow path 18 f from thesupply device through a pipe 23 a. The heat exchange medium supplied tothe flow path 18 f is returned to the supply device through a pipe 23 b.

The electrostatic chuck 20 is provided on the lower electrode 18. Whenthe substrate W is processed in the internal space 10 s, the substrate Wis placed on the electrostatic chuck 20 and is held by the electrostaticchuck 20.

The electrostatic chuck 20 has a main body and an electrode. The mainbody of the electrostatic chuck 20 is formed of a dielectric such asaluminum oxide or aluminum nitride. The main body of the electrostaticchuck 20 has a substantially disk shape. The central axis of theelectrostatic chuck 20 substantially coincides with the axis AX. Theelectrode of the electrostatic chuck 20 is provided in the main body.The electrode of the electrostatic chuck 20 has a film shape. Adirect-current power source is electrically connected to the electrodeof the electrostatic chuck 20 through a switch. When the voltage fromthe direct-current power source is applied to the electrodes of theelectrostatic chuck 20, an electrostatic attraction force is generatedbetween the electrostatic chuck 20 and the substrate W. Due to thegenerated electrostatic attraction force, the substrate W is attractedto and held by the electrostatic chuck 20.

The electrostatic chuck 20 includes a substrate placing area. Thesubstrate placing area is an area having a substantially disk shape. Thecentral axis of the substrate placing area substantially coincides withthe axis AX. When the substrate W is processed in the chamber 10, thesubstrate W is placed on the substrate placing area.

In an embodiment, the electrostatic chuck 20 may further include an edgering placing area. The edge ring placing area extends in acircumferential direction around the central axis of the electrostaticchuck 20 to surround the substrate placing area. An edge ring ER ismounted on the upper surface of the edge ring placing area. The edgering ER has a substantially plate shape and a ring shape. The edge ringER is placed on the edge ring placing area such that the central axisthereof coincides with the axis AX. The substrate W is disposed in anarea surrounded by the edge ring ER. That is, the edge ring ER isdisposed to surround the edge of the substrate W. The edge ring ER mayhave electrical conductivity. The edge ring ER is formed of, forexample, silicon or silicon carbide.

The plasma processing apparatus 1A may further include a gas supply line25. The gas supply line 25 supplies the heat transfer gas, for example,He gas, from a gas supply mechanism to a gap between the upper surfaceof the electrostatic chuck 20 and the back surface (lower surface) ofthe substrate W.

The plasma processing apparatus 1A may further include an insulatingregion 27. The insulating region 27 extends in the circumferentialdirection outside the substrate support 16 in the radial direction tosurround the substrate support 16. The insulating region 27 may extendin the circumferential direction outside the support 17 in the radialdirection to surround the support 17. The insulating region 27 is formedof an insulating material such as quartz. The edge ring ER is placed onthe insulating region 27 and the edge ring placing area of theelectrostatic chuck 20.

The plasma processing apparatus 1A further includes an upper electrode30. The upper electrode 30 is provided above the substrate support 16.The upper electrode 30 closes an upper opening of the chamber body 12together with a member 32. The member 32 has insulation properties. Theupper electrode 30 is supported on the upper portion of the chamber body12 through the member 32.

The upper electrode 30 includes a ceiling plate 34 and a support 36. Thelower surface of the ceiling plate 34 defines the internal space 10 s. Aplurality of gas discharge holes 34 a are formed in the ceiling plate34. Each of the plurality of gas discharge holes 34 a penetrates theceiling plate 34 in a plate thickness direction (vertical direction).The ceiling plate 34 is formed of for example, silicon. However, thereis no limitation thereto. Alternatively, the ceiling plate 34 may have astructure in which a plasma-resistant film is provided on the surface ofa member made of aluminum. This film may be a ceramic film such as afilm formed by anodization or a film formed of yttrium oxide.

The support 36 detachably supports the ceiling plate 34. The support 36is formed of a conductive material such as aluminum, for example. A gasdiffusion chamber 36 a is provided in the interior of the support 36. Aplurality of gas holes 36 b extend downward from the gas diffusionchamber 36 a. The plurality of gas holes 36 b communicate with theplurality of gas discharge holes 34 a, respectively. The support 36 hasa gas introduction port 36 c formed therein. The gas introduction port36 c is connected to the gas diffusion chamber 36 a. A gas supply pipe38 is connected to the gas introduction port 36 c.

A gas source group 40 is connected to the gas supply pipe 38 through avalve group 41, a flow rate controller group 42, and a valve group 43.The gas source group 40, the valve group 41, the flow rate controllergroup 42, and the valve group 43 configure a gas supply unit. The gassource group 40 includes a plurality of gas sources. Each of the valvegroup 41 and the valve group 43 includes a plurality of valves (forexample, on-off valves). The flow rate controller group 42 includes aplurality of flow rate controllers. Each of the plurality of flow ratecontrollers of the flow rate controller group 42 is a mass flowcontroller or a pressure control type flow rate controller. Each of theplurality of gas sources of the gas source group 40 is connected to thegas supply pipe 38 through a corresponding valve of the valve group 41,a corresponding flow rate controller of the flow rate controller group42, and a corresponding valve of the valve group 43. The plasmaprocessing apparatus 1A can supply the gas from one or more gas sourcesselected from the plurality of gas sources of the gas source group 40 tothe internal space 10 s at a flow rate individually adjusted.

A baffle plate 48 is provided between the substrate support 16 or thesupport 17 and the side wall of the chamber 10. The baffle plate 48 maybe configured, for example, by coating a plate material made of aluminumwith ceramic such as yttrium oxide. The baffle plate 48 has a pluralityof through-holes. An exhaust pipe 52 is connected to the bottom portionof the chamber 10 below the baffle plate 48. An exhaust device 50 isconnected to the exhaust pipe 52. The exhaust device 50 has a pressurecontroller such as an automatic pressure control valve, and a vacuumpump such as a turbo molecular pump, and can reduce the pressure in theinternal space IOs.

The plasma processing apparatus 1A further includes a radio frequencypower source 61. The radio frequency power source 61 is a power sourcethat generates radio frequency power HF. The radio frequency power HF isused to generate plasma from the gas in the chamber 10. The radiofrequency power HF has a first frequency. The first frequency is afrequency within the range of 27 to 100 MHz, for example 40 MHz or 60MHz. The radio frequency power source 61 is connected to the lowerelectrode 18 through a matching circuit 63 in order to supply the radiofrequency power HF to the lower electrode 18. The matching circuit 63 isconfigured to match the impedance on the load side (the lower electrode18 side) with the output impedance of the radio frequency power source61. In the embodiment in which the radio frequency power source 61 iselectrically connected to the lower electrode 18, the upper electrode 30is electrically grounded.

The plasma processing apparatus 1A further includes a bias power source62. The bias power source 62 is configured to supply a bias BE to thelower electrode 18 when plasma is being generated in the chamber 10 forplasma processing on the substrate W. The bias power source 62 iselectrically connected to the lower electrode 18 through a matchingcircuit 64. The matching circuit 64 is configured to match the impedanceon the load side (the lower electrode 18 side) with the output impedanceof the bias power source 62.

The bias BE is used to attract ions to the substrate W. The bias BE hasa second frequency. The bias BE is set to change the potential of thesubstrate W placed on the electrostatic chuck 20 within a cycle which isdefined by the second frequency. The second frequency is lower than thefirst frequency. The second frequency is a frequency within the range of50 kHz to 27 MHz, for example.

FIG. 3A is a diagram showing an example of the bias. As shown in FIG.3A, the bias BE may be radio frequency bias power having the secondfrequency. FIG. 4 is a diagram showing another example of the bias. Asshown in FIG. 4, the bias BE may be a pulsed negative voltage which isperiodically applied to the lower electrode 18 at the second frequency.

The plasma processing apparatus 1A further includes a power sourcedevice 70. The power source device 70 is configured to apply a positivevoltage to a conductive member. The conductive member extends closer tothe side wall of the chamber 10 than the substrate W placed on thesubstrate support 16. In an embodiment, the conductive member is theedge ring ER.

FIG. 3B is a timing chart showing an example of the potential of thesubstrate and the potential of the conductive member. As shown in FIG.3B, when the bias BE is supplied to the lower electrode 18, thepotential of the substrate W changes within the cycle which is definedby the second frequency. That is, the cycle which is defined by thesecond frequency includes a period in which the potential of thesubstrate W is negative and a period in which the potential of thesubstrate W is equal to or greater than 0. The period in which thepotential of the substrate W is negative and the period in which thepotential of the substrate W is positive are alternately repeated.

The power source device 70 is configured to apply a positive voltage tothe edge ring ER in the period in which the potential of the substrate Wis equal to or greater than 0, and set the potential of the edge ring ERin the period to a potential V_(A) (>V_(W)) higher than a potentialV_(W) of the substrate W. In an embodiment, the power source device 70includes a direct-current power source 70 a and a switch 70 b. Thedirect-current power source 70 a may be a variable direct-current powersource. The direct-current power source 70 a is connected to the edgering ER through the switch 70 b. When the switch 70 b is in a conductionstate, the voltage from the direct-current power source 70 a is appliedto the edge ring ER. The level of the positive voltage which is appliedto the edge ring ER and the application period of the positive voltageto the edge ring ER are specified by a controller MC. The level of thepositive voltage which is applied to the edge ring ER and theapplication period of the positive voltage to the edge ring ER may bedetermined in advance.

The plasma processing apparatus 1A further includes the controller MC.The controller MC is a computer which includes a processor, a storagedevice, an input device, a display device, and the like, and controlseach part of the plasma processing apparatus 1A. The controller MCexecutes a control program stored in the storage device, and controlseach part of the plasma processing apparatus 1A, based on recipe datastored in the storage device. The process designated by the recipe datais executed in the plasma processing apparatus 1A under the control bythe controller MC. In a case where the plasma processing apparatus 1A isused, the method MT may be executed by the control of each part of theplasma processing apparatus 1A by the controller MC.

Step ST2 is executed in a state where plasma is generated in the chamber10. In order to generate the plasma, a gas is supplied from the gassupply unit into the chamber 10. Further, the exhaust device 50 operatesto set the pressure in the chamber 10 to a designated pressure. Further,the radio frequency power HF is supplied. As a result, the gas in thechamber 10 is excited, so that plasma is generated from the gas. StepSTb is executed in a state where the plasma is generated in this manner.In step STb, the bias BE is supplied from the bias power source 62 tothe lower electrode 18. As a result, as shown in FIG. 3B, the potentialof the substrate W changes periodically. In a case where the plasmaprocessing apparatus 1A is used, in step ST2, a positive voltage isapplied from the power source device 70 to the edge ring ER.Specifically, a positive voltage is applied to the edge ring ER in theperiod in which the potential of the substrate W is equal to or greaterthan 0. The positive voltage sets the potential V_(A) of the edge ringER to a potential higher than the potential V_(W) of the substrate W inthe period in which the potential of the substrate W is equal to orgreater than 0.

Hereinafter, FIG. 5 will be referred to. FIG. 5 is a diagramschematically showing a plasma processing apparatus according to anotherexemplary embodiment. Hereinafter, a plasma processing apparatus 1Bshown in FIG. 5 will be described with respect to points different fromthe plasma processing apparatus 1A. The plasma processing apparatus 1Bdoes not have the power source device 70. In the plasma processingapparatus 1B, the bias power source 62 also serves as a power sourcedevice that applies a voltage to the edge ring ER. In the plasmaprocessing apparatus 1B, the bias power source 62 supplies radiofrequency bias power to the lower electrode 18. The lower electrode 18is connected to the edge ring ER through a variable impedance circuit72. The variable impedance circuit 72 may include, for example, avariable capacitance capacitor.

In the plasma processing apparatus 1B, the radio frequency bias powerwhich is supplied to the lower electrode 18 is branched into a firstpath from the lower electrode 18 to the substrate W through theelectrostatic chuck 20 and a second path from the lower electrode 18 tothe edge ring ER through the variable impedance circuit 72. Therefore,in the period in which the potential of the substrate W is equal to orgreater than 0, the voltage which is applied to the edge ring ER canalso have a positive polarity. Further, in the plasma processingapparatus 1B, the distribution ratio of the radio frequency bias powerbetween the first path and the second path is adjusted by adjusting theimpedance of the variable impedance circuit 72. The impedance of thevariable impedance circuit 72 is set such that the potential V_(A) ofthe edge ring ER becomes higher than the potential V_(W) of thesubstrate W within the period in which the potential of the substrate Wis equal to or greater than 0. The impedance of the variable impedancecircuit 72 can be designated by the controller MC. The impedance of thevariable impedance circuit 72 may be set in advance.

Hereinafter, FIG. 6 will be referred to. FIG. 6 is a diagramschematically showing a plasma processing apparatus according to stillanother exemplary embodiment. Hereinafter, a plasma processing apparatus1C shown in FIG. 6 will be described with respect to points differentfrom the plasma processing apparatus 1A. The plasma processing apparatus1C further includes a conductive member 74. The conductive member 74 isa member separate from the edge ring ER. The conductive member 74 isformed of a material having electrical conductivity, such as silicon.The conductive member 74 has a ring shape. The conductive member 74extends closer to the side wall of the chamber 10 than the substrate Wplaced on the substrate support 16. Specifically, the conductive member74 extends in the circumferential direction outside the edge ring ER inthe radial direction. The conductive member 74 is mounted on theinsulating region 27. In the plasma processing apparatus 1C, theposition in the height direction of the upper surface of the conductivemember 74 and the position in the height direction of the upper surfaceof the edge ring ER are substantially the same. The conductive member 74is separated from the edge ring ER. That is, the conductive member 74 iselectrically separated from the edge ring ER.

The plasma processing apparatus 1C includes a power source device 76instead of the power source device 70. The power source device 76 isconfigured to apply a positive voltage to the conductive member 74. FIG.7 is a timing chart showing an example of the potential of the substrateand the potential of the conductive member. The power source device 76is configured to apply a positive voltage to the conductive member 74 inthe period in which the potential of the substrate W is negative.Therefore, in the period in which the potential of the substrate W isnegative, the potential of the conductive member 74 becomes a positivepotential V_(C). In an embodiment, the power source device 76 includes adirect-current power source 76 a and a switch 76 b. The direct-currentpower source 76 a may be a variable direct-current power source. Thedirect-current power source 76 a is connected to the conductive member74 through the switch 76 b. When the switch 76 b is in a conductionstate, the voltage from the direct-current power source 76 a is appliedto the conductive member 74. The level of the positive voltage which isapplied to the conductive member 74 and the application period of thepositive voltage to the conductive member 74 are specified by thecontroller MC. The level of the positive voltage which is applied to theconductive member 74 and the application period of the positive voltageto the conductive member 74 may be determined in advance.

As described above, step STb and step ST2 are executed in a state whereplasma is generated in the chamber 10. In step STb, the bias BE issupplied from the bias power source 62 to the lower electrode 18. As aresult, as shown in FIG. 7, the potential of the substrate W changesperiodically. In a case where the plasma processing apparatus 1C isused, in step ST2, a positive voltage is applied from the power sourcedevice 76 to the conductive member 74. Specifically, a positive voltageis applied to the conductive member 74 in the period in which thepotential of the substrate W is negative.

FIG. 8 is a timing chart showing another example of the potential of thesubstrate and the potential of the conductive member. As shown in FIG.8, in an embodiment, the power source device 76 of the plasma processingapparatus 1C may apply a positive voltage to the conductive member 74 inboth the period in which the potential of the substrate W is negativeand the period in which the potential of the substrate W is equal to orgreater than 0. In the execution of step ST2, the power source device 76of the plasma processing apparatus 1C may continuously apply, forexample, a positive direct-current voltage to the conductive member 74in both the period in which the potential of the substrate W is negativeand the period in which the potential of the substrate W is equal to orgreater than 0.

FIG. 9 is a timing chart showing still another example of the potentialof the substrate and the potential of the conductive member. As shown inFIG. 9, in an embodiment, the power source device 76 of the plasmaprocessing apparatus 1C may apply a positive voltage higher than thepositive voltage which is applied to the conductive member 74 within theperiod in which the potential of the substrate W is equal to or greaterthan 0, to the conductive member 74 within the period in which thepotential of the substrate W is negative. In this example, the positivepotential V_(C) of the conductive member 74 within the period in whichthe potential of the substrate W is negative becomes higher than apositive potential V_(D) of the conductive member 74 within the periodin which the potential of the substrate W is equal to or greater than 0.

FIG. 10 is a timing chart showing still another example of the potentialof the substrate and the potential of the conductive member. As shown inFIG. 10, in an embodiment, the power source device 76 of the plasmaprocessing apparatus 1C may periodically or intermittently apply apulsed positive voltage to the conductive member 74 within the period inwhich the potential of the substrate W is negative.

Hereinafter, FIG. 11 will be referred to. FIG. 11 is a diagramschematically showing a plasma processing apparatus according to stillanother exemplary embodiment. Hereinafter, a plasma processing apparatus1D shown in FIG. 11 will be described with respect to points differentfrom the plasma processing apparatus 1C. The plasma processing apparatus1D further includes a power source device 70 as another power sourcedevice. The power source device 70 has the same configuration as thepower source device 70 of the plasma processing apparatus 1A.Specifically, the power source device 70 of the plasma processingapparatus 1D applies a positive voltage to the edge ring ER in theperiod in which the potential of the substrate W is equal to or greaterthan 0, and sets the potential V_(A) of the edge ring ER to a potentialhigher than the potential V_(W) of the substrate W in the period.

FIG. 12 is a timing chart showing an example of the potential of thesubstrate, the potential of the conductive member, and the potential ofthe edge ring. In a case where the method MT is executed by using theplasma processing apparatus D, as shown in FIG. 12, in step ST2, apositive voltage is applied from the power source device 76 to theconductive member 74. Even in a case where the plasma processingapparatus 1D is used, the positive voltage from the power source device76 is applied to the conductive member 74, similarly to the positivevoltage described with reference to FIGS. 7 to 10. That is, the positivevoltage from the power source device 76 is applied to the conductivemember 74 within at least the period in which the potential of thesubstrate W is negative. As a result, the potential of the conductivemember 74 becomes the positive potential V_(C) within the period inwhich the potential of the substrate W is negative. Further, in a casewhere the plasma processing apparatus 1D is used, in step ST2, thepositive voltage from the power source device 70 is applied to the edgering ER. The positive voltage from the power source device 70 is appliedto the edge ring ER in the period in which the potential of thesubstrate W is equal to or greater than 0. The positive voltage which isapplied to the edge ring ER sets the potential V_(A) of the edge ring ERto a potential higher than the potential V_(W) of the substrate W in theperiod in which the potential of the substrate W is equal to or greaterthan 0.

Hereinafter, FIG. 13 will be referred to. FIG. 13 is a diagramschematically showing a plasma processing apparatus according to stillanother exemplary embodiment. Hereinafter, a plasma processing apparatus1E shown in FIG. 13 will be described with respect to points differentfrom the plasma processing apparatus 1C. In the plasma processingapparatus 1E, the insulating region 27 has a raised portion raisedupward with respect to the edge ring ER outside the edge ring ER in theradial direction. The conductive member 74 is mounted on the raisedportion. Therefore, the position in the height direction of theconductive member 74 is higher than the position in the height directionof the edge ring ER and the position in the height direction of thesubstrate W.

Hereinafter, FIG. 14 will be referred to. FIG. 14 is a diagramschematically showing a plasma processing apparatus according to stillanother exemplary embodiment. Hereinafter, a plasma processing apparatus1F shown in FIG. 14 will be described with respect to points differentfrom the plasma processing apparatus 1C. In the plasma processingapparatus 1F, the conductive member 74 extends in the circumferentialdirection outside the upper electrode 30 in the radial direction. Theconductive member 74 is embedded in the member 32. The member 32 extendsbetween the upper electrode 30 and the side wall of the chamber 10.

Each of the plasma processing apparatus 1E and the plasma processingapparatus 1F may have the power source device 70 as another power sourcedevice, similarly to the plasma processing apparatus 1D. The powersource device 70 applies a positive voltage to the edge ring ER in theperiod in which the potential of the substrate W is equal to or greaterthan 0, and sets the potential V_(A) of the edge ring ER to a potentialhigher than the potential V_(W) of the substrate W.

While various exemplary embodiments have been described above, variousadditions, omissions, substitutions and changes may be made withoutbeing limited to the exemplary embodiments described above. Elements ofthe different embodiments may be combined to form another embodiment.

For example, the radio frequency power source 61 may not be connected tothe lower electrode 18 and may be connected to the upper electrode 30through the matching circuit 63. Further, in another embodiment, theplasma processing apparatus may be any type of plasma processingapparatus such as an inductively-coupled plasma processing apparatus, aslong as a positive voltage can be applied to the edge ring ER and/or theconductive member 74, as described above. Further, as the positivevoltage which is applied to the edge ring ER and/or the conductivemember 74 when plasma is being generated, the pulsed or continuouspositive direct-current voltage has been exemplified. However, thepositive voltage is not particularly limited. For example, the positivevoltage may be a voltage having any waveform such as a waveform which isobtained by combining a positive direct-current voltage with atriangular wave or the like. Further, when the plasma is not generated,a negative voltage may be applied to the edge ring ER and/or theconductive member 74.

From the foregoing description, it will be appreciated that variousembodiments of the present disclosure have been described herein forpurposes of illustration, and that various modifications may be madewithout departing from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

What is claimed is:
 1. A method of plasma processing comprising:preparing a substrate in a chamber of a plasma processing apparatus,wherein the substrate is disposed on a support in the chamber and thesupport includes a lower electrode and an electrostatic chuck providedon the lower electrode; and applying a positive voltage to a conductivemember extending closer to a grounded side wall of the chamber than thesubstrate, when plasma is being generated in the chamber for plasmaprocessing on the substrate.
 2. The method according to claim 1, whereinthe substrate is disposed on the support and in an area surrounded by anedge ring, the method further comprises supplying a bias to the lowerelectrode when the plasma is being generated in the chamber for theplasma processing on the substrate, the edge ring is the conductivemember, the bias is radio frequency bias power or a pulsed negativevoltage which is periodically applied to the lower electrode, and thepositive voltage is applied to the edge ring in a period in which apotential of the substrate is equal to or greater than 0, and sets apotential of the edge ring to a potential higher than the potential ofthe substrate in the period.
 3. The method according to claim 1, whereinthe substrate is disposed on the support and in an area surrounded by anedge ring, the conductive member is electrically separated from the edgering and extends closer to the side wall of the chamber than the edgering, the method further comprises supplying a bias to the lowerelectrode when the plasma is being generated in the chamber for theplasma processing on the substrate, the bias is radio frequency biaspower or a pulsed negative voltage which is periodically applied to thelower electrode, and the positive voltage is applied to the conductivemember in a period in which a potential of the substrate is negative. 4.The method according to claim 3, wherein the positive voltage is appliedto the conductive member even in a period in which the potential of thesubstrate is equal to or greater than
 0. 5. The method according toclaim 4, wherein the positive voltage is a direct-current voltage whichis continuously applied to the conductive member in both the period inwhich the potential of the substrate is negative and the period in whichthe potential of the substrate is equal to or greater than
 0. 6. Themethod according to claim 4, wherein the positive voltage applied to theconductive member in the period in which the potential of the substrateis negative is higher than the positive voltage applied to theconductive member in the period in which the potential of the substrateis equal to or greater than
 0. 7. The method according to claim 3,wherein a positive voltage is applied to the edge ring to set apotential of the edge ring to a potential higher than the potential ofthe substrate in a period in which the potential of the substrate isequal to or greater than
 0. 8. The method according to claim 1, whereinthe plasma processing is plasma etching on the substrate.
 9. Anapparatus for plasma processing comprising: a chamber; a substratesupport provided in the chamber and including a lower electrode and anelectrostatic chuck provided on the lower electrode; and a power sourcedevice configured to apply a positive voltage to a conductive memberextending closer to a grounded side wall of the chamber than a substrateplaced on the substrate support.
 10. The apparatus according to claim 9,further comprising: a bias power source configured to supply a bias tothe lower electrode when plasma is being generated in the chamber forplasma processing on the substrate. wherein the bias is radio frequencybias power or a pulsed negative voltage which is periodically applied tothe lower electrode, the conductive member is an edge ring extending tosurround the substrate, and the power source device is configured toapply the positive voltage to the edge ring in a period in which apotential of the substrate is equal to or greater than 0, and set apotential of the edge ring to a potential higher than the potential ofthe substrate in the period.
 11. The apparatus according to claim 9,further comprising: the conductive member extending closer to a sidewall of the chamber than an edge ring extending to surround thesubstrate placed on the substrate support; and a bias power sourceconfigured to supply a bias to the lower electrode when plasma is beinggenerated in the chamber for plasma processing on the substrate, whereinthe bias is radio frequency bias power or a pulsed negative voltagewhich is periodically applied to the lower electrode, and the powersource device is configured to apply the positive voltage to theconductive member in a period in which a potential of the substrate isnegative.
 12. The apparatus according to claim 11, wherein the powersource device is configured to apply the positive voltage to theconductive member even in a period in which the potential of thesubstrate is equal to or greater than
 0. 13. The apparatus according toclaim 12, wherein the power source device is configured to continuouslyapply a direct-current voltage as the positive voltage to the conductivemember in both the period in which the potential of the substrate isnegative and the period in which the potential of the substrate is equalto or greater than
 0. 14. The apparatus according to claim 12, whereinthe positive voltage applied to the conductive member in the period inwhich the potential of the substrate is negative is higher than thepositive voltage applied to the conductive member in the period in whichthe potential of the substrate is equal to or greater than
 0. 15. Theapparatus of claim 11, further comprising another power source deviceconfigured to apply a positive voltage to the edge ring in a period inwhich the potential of the substrate is equal to or greater than 0, toset a potential of the edge ring to a potential higher than thepotential of the substrate in the period in which the potential of thesubstrate is equal to or greater than 0.